1. Field of the Invention
The present invention generally relates to data networks. More specifically, the invention relates to the configuration of routers, switches and other network devices within such data networks.
2. Description of Related Art
Several limitations may be encountered when configuring networks such as local area networks, storage area networks and the like. There are a variety of network devices, such as routers, switches, bridges, etc., which may be used to configure such networks. Some of these network devices have greater capabilities than others. For example, some devices may readily be configured to support logical networks superimposed upon a physical network (e.g., virtual local area networks (“VLANs”) or virtual storage area networks (“VSANs”)) and some may not.
In order to allow multiple VLANs to share a single inter-switch link on the underlying physical topology, the interswitch link protocol (“ISL”) was developed at Cisco Systems. See for example U.S. Pat. No. 5,742,604, entitled “Interswitch link mechanism for connecting high-performance network switches,” Edsall, et al., issued on Apr. 21, 1998 to Cisco Systems, Inc., which is hereby incorporated by reference for all purposes. ISL provides an encapsulation mechanism for transporting packets between ports of different switches in a network on the basis of VLAN associations among those ports
In one example, it would be useful to transport packets of different frame types using the same inter-switch link instead of dedicating inter-switch links for different frame types. For example, it would be desirable if links between network devices could carry both Ethernet and Fiber Channel (“FC”) frames.
It is also important to determine as quickly as possible whether a network device has certain capabilities. For example, it would be very useful to determine quickly whether a peer port of another network device is configured (or could be configured) to carry frames of particular VLANs or VSANs, and to configure the network device as needed. Otherwise, various problems (including dropped frames) will ensue if the network device is connected to other devices that are transmitting frames for the wrong VLAN or VSAN. However, testing and configuring network devices for such capabilities can be time-consuming.